Femtocell access point devices are radio access point devices that are deployed at subscriber sites in order to improve coverage of mobile wireless communication service (e.g., cell phone, wireless messaging, etc.) and thereby offload the burden on the infrastructure of the mobile service provider. Femtocell access points are essentially cellular transceiver towers. Like cell towers, femtocell access points operate in a licensed spectrum that is subject to strict regulatory constraints on service providers. For example, a femtocell access point should not transmit on a frequency that is not licensed by a service provider in a given location. The Federal Communication Commission (FCC) requirements in the United States are particularly strict and a service provider may have licensed different frequencies in different parts of the country. As a result of this regulatory environment, femtocell access point deployments require ongoing location verification.
Techniques to perform location verification typically involve two mechanisms: Global Positioning System (GPS) based location and radio network scan. GPS location techniques require a line-of-sight from the femtocell access point device to the sky and the GPS receiver in the femtocell access point has to “lock” to signals from several different satellites in order to obtain an accurate GPS location. Moreover, a GPS location procedure may require up to 20 minutes (or longer) in order to lock to signals from the satellites. The use of an external antenna partially alleviates the line-of-sight issues. However, the relatively long period of time needed to lock to the satellites is undesirable, particularly when the femtocell access point device is rebooting and cannot resume serving devices in the wireless network until the location has been verified on reboot.
The radio scan function of the femtocell access point allows it to listen to its radio environment and detect neighbor cellular transceivers. Neighbor cellular transceiver “towers” transmit signals that contain basic information, such as country, network and cellular transceiver identification. At a basic level, the radio scan function allows a femtocell access point to ascertain that it is in the right country and in the neighborhood of the correct “macro” cell(s). However, this information alone may not be sufficient to determine the precise geographic location of the femtocell access point device and the corresponding frequency on which the femtocell access point should operate.